How to use DWDM system to expand the network?
2017-03-30

Dense Wavelength Division Multiplexing (DWDM) network is the most effective and feasible solution to achieve long-distance fiber expansion, which has been widely recognized by the people. In practice application, apart from increasing network bandwidth, we also need to focus on the fact that how to use DMDW system to extend the transmission distance of the network.

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DWDM optical module - An important factor affecting the transmission distance

As we all know, the transmission distance of the optical network will be affected by date rate, optical loss etc. factors. Different specifications of DWDM have different supporting transmission distances. For example, the theoretical transmission distance of 1G DWDM SFP optical modules on the market can reach 100km, while the transmission distance of 10DWDM SFP+ optical module is theoretically up of 80km, so it is very important to choose a kind of optical module that meets the practical needs. However, in the some cases, we may need to extend the transmission distance of the network without replacing optical module, so that some other devices will be required to ensure the transmission quality of the optical signal. Here we will take the DWDM network of 10G DWDM SFP+ optical module as an example to explain the fact that how to extend transmission distance by increasing devices.
DWDM SFP

Instance 1: 40km DWDM network

As mentioned above, the theoretical transmission distance of 10G DWDM SFP+ optical modules on the market can reach 80km, so if there are no other facilities in the DWDM network, we can easily build 40km DWDM network without increasing other devices between two DWDM multiplexer / demultiplexer, and the data transmission rate of the network can reach 10Gbps.

40km DWDM network

Instance 2: 80km DWDM network

Although the longest transmission distance of 10G DWDM SFP+ optical module is up to 80km, due to the optical signal will cause loss during the transmission process, to ensure the receiving quality of the optical signal, we usually need to deploy pre amplifier (PA) in front of the optical receiver to improve its reception sensitivity. In addition, also dispersion compensation module (DCM) can be used to process the accumulated dispersion in the link in the case do not regenerate the wavelengths in the link anymore. The following diagram is a concrete example of this network:

80km DWDM network

Instance 3: 120km DWDM network

As we know, the longer transmission distance, the more loss will be caused. If we want to use 10G DWDM SFP+ optical module in the DWDM network with a transmission distance of 120km, multiple optical amplifiers must be increased, as shown below, apart from deploying PA and DCM, BA is also necessary to be added on the multiplexer end to ensure the transmission distance of the optical signal up to 120km.

120km DWDM network

The three instances above are simple construction diagrams of DWDM networks, we need to pay special attention to the optical loss and the budget of the dispersion compensation in the practical application. Whichever kind of DWDM network you want to build, the optical communication products below have to be used:

optical communication products
It should be noted that the transmission distance of the DWDM network is not limited to the 120km mentioned in this article, but can be extended to 170km, or even 200km.
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